Generic semantic equality and order. The semantic order referred
to is that of a typical CPO for Haskell types, where e.g. (True,
bottom) <=! (True, False), but where (True, True)
and (True, False) are incomparable.

The implementation is based on isBottom, and has the same
limitations. Note that non-bottom functions are not handled by any
of the functions described below.

One could imagine using QuickCheck for testing equality of
functions, but I have not managed to tweak the type system so that
it can be done transparently.

x \/! y and x /\! y compute the least upper and greatest
lower bounds, respectively, of x and y in the semantical
domain ordering. Note that the least upper bound may not always
exist.
This functionality was implemented just because it was
possible (and to provide analogues of max and min in the Ord
class). If anyone finds any use for it, please let me know.